Abstract Bullying is all too common in the early school years, occurring at approximately the same rate in Kindergarten and 1st (K1) grades as in later elementary school. Research underscores how bullying at an early age is predictive of continued bullying and peer victimization, and how all involved?bullies, victims, and bystanders? are at elevated risk for negative outcomes in many aspects of a child's social, emotional, and academic life. Recent reviews of school-based programs demonstrate that punitive, disciplinary approaches to bullying prevention do not work, and that social emotional learning (SEL) is a critical ingredient in effective programs. Unfortunately, logistical barriers (e.g., time, cost, need for trained staff) too often undermine schools' abilities to implement traditional in-person SEL strategies with all students. This SBIR Fast-Track will leverage cutting- edge intelligent social tutoring game technology to create a new, evidence-based serious game specifically designed to help younger students develop the social emotional skills they need to navigate bullying situations. 3C Institute is a leader in the field of game-based Intelligent Social Tutoring Systems (ISTS) with extensive experience creating and testing SEL games. 3C's ongoing collaboration with the Bellevue Public School in WA, Communities in Schools-Wake County Public Schools, NC, and our commercialization partner, Personalized Learning Games, will provide a solid foundation on which to build, test, and commercialize the proposed serious K1 SEL game product. Five specific aims will be accomplished. In Phase I, we will (1) create a serious game prototype based on input from K1 students, parents, and educators with a custom graphic design and storyworld and five prototype social problem solving (SPS) scenes. We will also (2) conduct end user tests with K1 students and educators who will review and evaluate the prototype. In Phase II, we will (3) develop the full product through an iterative testing process for a total of 25 SPS scenes aligned to CASEL's SEL framework (Self-management, Self-awareness, Social Awareness, Relationship Skills, & Responsible Decision Making) as well as online Student, Home, and Educator Portals. Then, we will (4) conduct a randomized active control pilot study to test the serious game's impact for improving K1 students' social emotional behavior, ability to problem solve in bullying situations, self-efficacy for coping with bullying, and awareness of behaviors that constitute bullying. We expect the SEL serious game to result in significant improvements in all areas compared to the active control group. Lastly, we will (5) prepare for commercialization by conducting focus groups with educators to finalize the complete product and formulate implementation guidelines for schools. We will also develop all needed online training demos and materials, finalize online reporting functions, and integrate e-commerce functions into the website. Our proposed product will meet a significant market need as the first rigorously tested serious game for SEL bullying prevention with younger students. We have already secured a pathway to market, with Personalized Learning Games, Inc. committed to offering the product.